It is known to provide caching in a mobile network. Caching is based on the idea that a large percentage of Internet traffic is repetitive, and that eliminating the sending of repeating content from its origin may offer a savings opportunity in terms of required bandwidth. The main principle of caching in a mobile network is that copies of the repeated content in, for example, the Internet, are moved closer to mobile users. For example, such content may be cached in different parts of the Radio Access Network (RAN), in the Core Network (CN), or just “above” the CN.
The main benefits that can be achieved with caching in mobile networks are as follows:
a. A decrease in the cost of transport in the mobile network as well as the cost for Internet peering. This is achieved “above the cache”, as the cached information in principle is only transferred once in the transmission links above the cache.
b. An improved quality of experience for the mobile end-users. This is mainly achieved with lower delays, as the cached information can be returned faster to the mobile users from the cache (compared to the case where the information is obtained all the way from the original location).
c. Provision of new services, such as content hosting and storage/backup for the operators. A mobile operator can agree with content providers to ensure that the content from a specific content provider is delivered in a better way to the mobile users in the mobile operator's network.
Caching can also be used for the media distribution towards the mobile users. Instead of retrieving downloadable media from the media server or from other users, the media can be retrieved from the cache. FIG. 1 shows how media information from a media server 1 that has access to several media sources 1a is pushed in to a cache 2 in a mobile network 3 and then the mobile users 4, 5 can receive the media information directly from the cache 2 instead of from the media server 1. Note that that caching can be used for almost any type of internet content, and so the example of media content shown in FIG. 1 could be replaced with almost any other type of content.
Common RAN caching is about including a cache 2 in the RAN for all different radio access technologies, for example GSM, WCDMA and LTE. A good placement for a RAN cache is at a common RAN Controller, for example a node that includes either a Base Station Controller (BSC) or Radio Network Controller (RNC) or both. A challenge for caching is to ensure that the user plane traverses via the RAN cache. If the cache is included in the RNC, then the WCDMA/HSPA user plane automatically traverses via the RAN cache. The same applies for GPRS/EDGE user plane traffic where the RAN cache is included at the BSC. However, in the latter case there is an additional challenge as the GPRS/EDGE user plane traffic is normally encrypted between the MS/UE and the Serving GPRS Support Node (SGSN) and therefore the traffic is encrypted when traversing through the BSC.
A problem arises then using the Long Term Evolution (LTE) architecture. LTE is a communication network technology currently under development by the 3rd Generation Partnership Project (3GPP). LTE requires a new radio access technique termed Evolved Universal Terrestrial Radio Access Network (E-UTRAN), which is designed to improve network capacity, reduce latency in the network, and consequently improve the end-user's experience. System Architecture Evolution (SAE) is the core network architecture for LTE communication networks.
As shown in FIG. 2, LTE is a so called “flat RAN architecture” without any RAN controller. The control plane interface (S1-MME) goes directly between an eNodeB (eNB) 6 and a Mobility Management Entity (MME) 7, and the user plane interface (S1-U) goes directly between the eNB 6 and a Serving GW (SGW) 8. Note that the SGW 8 can be integrated together with a PDN GW, but for simplicity, the term SGW is used herein to denote the user plane gateways in the core network. To enable caching, the user plane interface needs to be routed via a RAN Controller 9, shown as the thick black line between the eNB 6, the cache 2 and the SGW 8, and the textbox “How?”
As LTE is a flat RAN architecture, there is at present no way of ensuring that user plane traffic traverses the RAN controller 9 and hence can access the RAN cache 2.
Furthermore, the same problem applies to other circumstances in which it is desirable for user plane traffic to traverse a particular node. For example, instead of the caching problem described above, it may be required for traffic to traverse a particular node that provides “cloud” applications and/or software hosting. Similarly, user plane traffic optimization or packet inspection may be required in the node. In any of these exemplary cases, there is currently no way of ensuring that user plane traffic is routed via a particular node located between the eNB 6 and the SGW 8.